Arsenal manager Arsene Wenger accused his side of under-estimating Birmingham City after losing top spot in the table on the back of their 1-1 draw at the Emirates Stadium.
The Gunners had looked on course to secure another home victory when Emmanuel Adebayor's penalty put them one up midway through the first half.
But Garry O'Connor's equaliser via a deflected header from a corner left Wenger frustrated and his players on the end of a critical appraisal of their performance.
He said: "It was very frustrating. The crowd pushed us on but we were punished for losing concentration on the set-piece.
"We thought it was going to be too easy, but we didn't create enough overall. We were not sharp enough and they defended well. It's as simple as that."
However, Wenger denied claims that the dropped points would be a major blow to their title aspirations.
"Every game is important so it's hard to say which is the crucial month, but today we lost two points we shouldn't have lost," he added.
"I'm confident the team will re-focus because they are very disappointed. The focus today wasn't good enough."